In LTE (Long Term Evolution) systems specified in the 3GPP (3rd Generation Partnership Project), in uplink is adopted SC-FDMA (Single-Carrier Frequency Division Multiple Access) which actualizes low Peak-to-Average Power Ratio (PAPR) and is effective at increasing coverage. Accordingly, by scheduling in a radio base station apparatus (BS: Base Station), basically, the base station allocates radio resources of some frequency and some time to a single mobile terminal apparatus (UE: User Equipment), and therefore, users in the same cell are orthogonal to one another in the frequency domain and time domain. However, in the LTE systems, since one cell frequency reuse is a base, interference from peripheral cells is large, and particularly, an interference level from a UE present at the cell edge is high. Therefore, measures against inter-cell interference are required in order to compensate for such peripheral cell interference and maintain certain reception quality.
As inter-cell interference measures, the role performed by uplink transmission power control is significant, and in consideration of propagation loss between a user and a radio base station apparatus, and interference imposed on peripheral cells, the radio base station apparatus is required to control transmission power of mobile terminal apparatuses so as to meet required reception quality. In the LTE systems, Factional transmission power control is adopted as the transmission power control method with consideration given to inter-cell interference.
More specifically, transmission power of signals (PUSCH (Physical Uplink Shared CHannel), PUCCH (Physical Uplink Control CHannel), SRS (Sounding Reference Signal)) and the like transmitted in uplink in the LTE systems is controlled by a combination of open-loop control by parameters (P0, α, etc.) notified by a radio base station apparatus at relatively long intervals and propagation loss (PL) measured by a mobile terminal apparatus, and closed-loop control by a TPC command notified by the radio base station apparatus at relatively short intervals based on communication conditions (for example, reception SINR (Signal to Interference plus Noise power Ratio) in the radio base station apparatus) between the radio base station apparatus and the mobile terminal apparatus. More specifically, transmission power of the PUSCH is given by following equation (1) (for example, see Non-patent Document 1).PPUSCH(i)=min{PCMAX,10 log 10(MPUSCH(i))+P0—PUSCH(j)+α(j)·PL+ΔTF(i)+f(i)}  Eq. (1)Herein, PCMAX is maximum transmission power, MPUSCH is a transmission bandwidth, P0—PUSCH is a parameter related to target reception power, α is a weighting factor of Fractional TPC, PL is a path loss measurement value, ΔTF is an offset dependent on MCS, and f(i) is a correction value by a TPC command.
In this Fractional transmission power control, target reception power is set (achieved by the parameter a of open-loop control) corresponding to the propagation loss (PL) in the mobile terminal apparatus, and it is thereby possible to reduce inter-cell interference.
Further, in closed-loop TPC performed between the radio base station apparatus and the mobile terminal apparatus, for example, the radio base station apparatus measures a difference between the reception SINR obtained by averaging for averaging time t and the target reception SINR, notifies the mobile terminal apparatus of the difference as a TPC command, and thus controls transmission power of the mobile terminal apparatus.